Injection type fuel feeder

ABSTRACT

An injection type fuel feeder for automotive vehicles in which the injection time of the fuel is computed on the basis of conditional signals from the engine, which include engine revolutions per minute, temperature, etc., in combination with a saw-tooth current, characterized in that the rate of change of the saw-tooth current is controlled in accordance with the engine manifold negative pressure and the temperature of the engine, whereby compensation of the engine output and temperature can be accomplished in proportion to the other conditional signals.

111111 States atent 1191 1111 3,242,919 Suda 1 .iuiy 3, 1973 [541INJECTION TYPE FUEL FEEDER 3.372680 3/1968 SChOII 123/32 EA 75 I I S3,456,628 7/1969 131158616161. 123/32 EA I I memo Sud, M110 v 3,464,3969 1969 Scholl 123/32 EA [731 Assignee: Hitachi, Ltd., Tokyo, Japan [22]Filed: 14 1970 Primary Examiner-Laurence M. Goodridge AssistantExaminer-Cort Flint Attorney-Craig, Antonelli, Stewart & Hill [30]Foreign Application Priority Data Dec. 12, 1969 Japan .......44/99435[57] ABSTRACT I An injection type fuel feeder for automotive vehicles in[52] [1.8. CL... 123/32 EA, 123/119 R, 123/140 M which the injectiontime of the fuel is computed on the [51] Int. Cl. FOZd 5/00 basis ofConditional Signals from the engine which Field of Search l d gi l ti pi t t p t t in combination with a saw-tooth current, characterized R inthat the rate of change of the saw-tooth current is [56] eferences Citedcontrolled in accordance with the engine manifold neg- UNITED STATESPATENTS ative pressure and the temperature of the engine, 3,612,00910/1971 Kamazuka 123/32 EA whereby compensation of the engine output andtem- 36 5240 2/1972 np tit 3/3 A perature can be accomplished inproportion to the Douglas other onditional signals 3,272,187 9/1966Westbrook et al.. 123/32 EA 3,314,407 4/1967 Schneider 123/148 E 11Claims, 10 Drawing Figures I 1 7 NEG PRESS ADDED SIG LE- M FUEL INJDETECTING VEL DETECTING VALVE 1 REV NO.

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SEun SuDn BY l gx RM} HTTO RN EYS INJECTION TYPE FUEL FEEDER BACKGROUNDOF THE INVENTION This invention relates to injection type fuel feedersfor automotive vehicle engines and more specifically to injection fuelfeeders capable of effectively adjusting the fuel feed from aneconomical output region to the high output region of such engines tocompensate for various engine conditions.

Generally, the injection fuel feeder associated with electrical controlmeans is operated in such a manner that the conditions for determiningthe fuel feed to an internal combustion engine are converted intoelectric signals, from which an output signal having a time widthcorresponding to the amount of fuel to be supplied to the engine isderived through computation, the fuel injection valve then being openedby said output signal to insure that an adequate amount of fuel is supplied to the engine based on a function of time.

The present invention provides such an injection fuel feeder arrangementwhich serves to control the amount of fuel supplied to the engine as afunction of time in accordance with such engine conditions as enginespeed in revolutions per minute, engine temperature and manifoldpressure. More particularly, the present invention provides such controlover the fuel injection by relatively simple and reliable means whicheffect a smooth control on a continuous basis between respective feedrates based on manifold pressure.

It is an object of the present invention to provide a fuel injectioncontrol system of the type described which provides for improvedperformance over those systems known heretofore.

It is another object of the present invention to provide a fuelinjection control system which is capable of effecting smooth control ona continuous basis with switching between first and second fuel rates inresponse to manifold pressure.

It is a further object of the present invention to provide a fuelinjection control system which is capable of response to a plurality ofconditions, but is simple, reliable and inexpensive.

These and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription thereof when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a block diagram showing a conventional electric control systemfor an injection type fuel feeder;

FIG. 2 is a schematic circuit diagram showing a conventional controlcomputing means;

FIGS. 3(a) and 3(b) are characteristic diagrams explaining the operationof the circuit of FIG. 2;

FIG. 4 is a diagram showing the characteristics of fuel feed versusengine manifold negative pressure;

FIG. 5 is a schematic circuit diagram showing another conventionalcontrol computing means;

FIG. 6 is a diagram showing the fuel feed characteristics of aninjection fuel feeder embodying this invention;

FIG. 7(a) and 7( b) are diagrams which aid in explanation of the controloperation characteristics of the present invention; and

FIG. 8 is a schematic circuit diagram of a control arrangement inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, there isshown a fuel feeder including a plurality of engine condition detectorscomprising a negative pressure detector 1 for converting the enginemanifold negative pressure P into an electric condition signal; anengine speed detector 2 for converting the number of engine revolutionsper minute (r.p.m.) N into an electric condition signal; a temperaturedetector 3 for converting the engine temperature T into an electriccondition signal; a trigger pulse generator 4 for generating a signal ata desired time for triggering the condition signals of detectors 1, 2and 3 to start fuel injection into the engine; and a time signalgenerator 5 actuated by the trigger signal of generator 4 to generate asawtooth wave time signal. An adding signal level detector 6 receivesthe outputs from the detectors 1, 2 and 3, and is also supplied with thetime signal from the generator 5, thus producing an output with a timewidth starting from the time at which the trigger signal is generated tothe time at which the sum of the condition signals and time signalreaches a particular detection level. A fuel injection valve 7 is openedin response to the output signal from the detector 6, whereby thenecessary amount of fuel is supplied to the engine.

In the above-described arrangement, a circuit comprising an Esaki diode8 and a transistor 9, as shown in FIG. 2, is effectively used for saidlevel detector 6. The Esaki diode 8 is connected in parallel between thebase and emitter of the grounded-emitter transistor 9 with the samepolarity direction. The collector of transistor 9 is connected to anoutput terminal 10 and also to a power source circuit 12 via a resistor11; and, the base of the transistor is connected to an input terminal13, to which a negative detection signal voltage E revolution numberdetection signal voltage E temperature detection signal voltage E andtime signal voltage E, are applied via resistors 14, 15, 16, and 17. Inaddition, a trigger signal terminal 4' receiving the output of pulsegenerator 4 is connected to the input terminal 13.

When the current flowing to the base of transistor 9 and through diode 8due to the conditional signal voltages relating to the engine conditionsbeing monitored is smaller than the peak value of the Esaki diode 8, theforward impedance of the Esaki diode will be very small and,accordingly, the current due to the conditional signals can be addedtogether without interfering with each other. Also, because the terminalvoltage across the diode is small, compared with the barrier voltage ofthe transistor 9, the collector voltage will be high, and an outputvoltage can be derived from the output terminal 10.

In the above circuit, when the time signal voltage E, is made zero bythe trigger signal at a desired time for starting fuel injection and, atthe same time, the current flowing in the Esaki diode due to thecombined conditional signal voltages is maintained at a level lower thanits peak value, an output signal is derived at the output terminal 10and the fuel injection valve 7 is opened. However, when the combinedcurrent flowing due to the added conditional signal voltages and thetime signal voltage E which increases with time, becomes more than thepeak value of the Esaki diode 8, the transistor 9 immediately becomessufficiently biased to turn on and thus becomes conductive, whereby thesupply fuel is stopped because the output voltage at the output terminalwhich controls the fuel injection valve 7 vanishes. Thus, the durationof the fuel feeding period depends on the level of the conditionalsignal current, and hence, the amount of the injected fuel supply can becontrolled according to the conditions of the engine. This operationwill be more specifically described with reference to FIGS. 3(a) and3(b).

In FIG. 3(a), it is assumed that I, denotes the signal current flowingfor the period t from the time at which the fuel injection is desired tobe started, and I, indicates the conditional signal current. Then, thecombined current (I, I,) flowing into the Esaki diode 8 form the inputterminal 13 should become I,,. When the time is zero at the start offuel injection, operated in the region within the peak value I by thetrigger signal. Therefore, an output signal voltage E is delivered atthe output terminal 10 as shown in FIG. 3(b), in the region wherein thecombined current I is smaller than the peak value I,,. When the combinedcurrent I reaches the peak value 1,, of the Esaki diode 8, the terminalvoltage across the Esaki diode 8 is rapidly increased, and thebase-emitter bias of the transistor 9 becomes sufficiently large torender the transistor 9 conductive. At this time t the output signalvoltage B vanishes. Thus, the amount of fuel supply can be determined asa function of time t,.

When the conditional signal current T, is changed to a conditionalsignal current I, due to a condition change of the engine, the combinedcurrent I is accordingly changed to I,,. As a result, the time t, takenfor the Esaki diode 8 to reach its peak value I, is changed to and theamount of fuel supply is also changed due to the resulting variation inthe period of opening of the injection valve 7. In other words, the fuelfeed is controlled according to engine conditions.

The fuel feed Q at an engine manifold negative pressure P should becontrolled so as to be increased in the region of small engine manifoldnegative pressure P, as seen in FIG. 4. More specifically, the region inwhich the engine manifold negative pressure P is relatively largerepresents the medium output region or, in other words, this region isthe normal operating region of the motor vehicle engine. In this region,the fuel feed Q is determined from an economical point of view. On theother hand, the region in which the engine manifold negative pressure issmall is indicative of the need for a large output form the engine. Inthis region, therefore Q is determined so as to be able to deliver themaximum output without taking requirements of economy intoconsideration.

The desired characteristics for a fuel feed operation as described abovecan be obtained through the arrangement as illustrated in FIG. 5,wherein the resistors 14 and for applying a negative pressure detectionsignal voltage [3,, and revolution number detection signal voltage E tothe input terminal 13 are changed over to the resistors 14' and 15',respectively, by the switching contacts 18 and I9 actuated in accordancewith the engine manifold negative pressure P, and the fuel feed iscontrolled according to the resistance values of the resistors 14 and15'. In this arrangement, the conversion coefficient of the conditionalsignal current can be changed by changing said resistance values. On theother hand, however, the absolute value of the conversion coefficient isinevitably changed abruptly with this arrangement to thereby cause askip in the control and introduce a shock into the normal flow of fuel.

To avoid this, it is necessary to provide an arrangement wherein a biassignal voltage E in addition to the conditional signal, is appliedthereto and this bias signal voltage is switched from the resistor 21 tothe resistor 21' by way of contact 20, whereby the skip is reduced. Thisarrangement, however, requires a large number of switching contacts andis unavoidably complicated in composition and short in life.Furthermore, this type of conventional device is undesirable from thestandpoint of reliability because shocks are still generated due to thisdiscontinuous operation.

The principles and an embodiment of the present invention will bedescribed below by referring to FIGS. 6 through 8. The fuel feedcharacteristics which have been described by referring to FIG. 4 areones determined from design requirements. Substantially, the fuel feedcharacteristics at the engine manifold negative pressure P for themaximum output is indicated by the dotted line 1 and for the economicaloutput by the dotted line 12, as shown in FIG. 6. Therefore, to changeover the operating characteristics from for the maximum output toanother for economical output at the engine manifold negative pressureP,, it is ideal to employ the characteristic shown by the full line Itis desirable that the characteristic change-over from the dotted lines 1to 12 be done continuously with a certain time lag so as not to cause anoperating shock. This fuel feed characteristic change-over can berealized by suitably deterrnining the conversion coefficient of the timesignal versus time lapse in the manner described above with reference toFIGS. 1 through 3. For example, the conversion coefficient of the timesignal is changed over at the engine manifold negative pressure P, sothat the time signal current I, is switched to I, as shown in FIG. 7(a),and the conversion coefficient of the time signal current I, isdetermined so that the fuel feed characteristics at the engine manifoldnegative pressure P take the form of the dotted line 1 and that of I, isdetermined so that the fuel feed characteristics take the form of 12. Bythis arrangement, the time taken for the Esaki diode 8 to reach its peakvalue I from the combined current I of the conditional current I, andtime signal current I,(I,') at the engine manifold negative pressure P,is changed over to t from t,, and thus an output signal voltage E asshown in FIG. 7(b) is obtained.

When the time signal current I, is changed over to I, continuously witha time lag, then the characteristic change-over can be accomplishedwithout causing a shock.

This change-over operation will be more specifically described byreferring to FIG. 8 wherein an exemplary embodiment of the detector 5 inaccordance with this invention is illustrated. The reference 22 denotesa PNP transistor controlled at a constant current. The emitter of thistransistor is connected to a power source line 24 via a resistor 23, andthe collector is connected to an output terminal 25 and also to groundvia a capacitor 26. The base of transistor 22 is connected to the powersource line 24 via a resistor 27 and also to the voltage dividing pointbetween voltage dividing resistors 29 and 30 via a zener diode 28, theresistors 29 and 30 being connected in series between the power line 24and ground. A compensating resistor 31 is connected in parallel to thevoltage dividing resistor 29 through switch 32, which is closed when theengine manifold negative pressure P is below the value P, by a diaphragm33 operated by the engine manifold negative pressure P. A delaycapacitor 34 is connected in parallel to the voltage dividing resistor30. The purpose of this delay capacitor is to prevent abrupt voltagevariation produced at the voltage dividing point when the switch 32 isactuated. The numeral 35 represents an NPN transistor for returning thevoltage at the time signal output terminal to zero at a desired time soas to start fuel injection again; the collector is connected to thepower line 24 via a resistor 36 and is connected in the forwarddirection to the collector of the transistor 22 via a diode 37. The baseof the transistor is connected to a trigger input terminal 39 via aresistor 38.

In the region in which the engine manifold negative pressure P is largerthan the set value P,, the terminal voltage of the voltage dividingresistor 29 is large. Ac-

p cordingly, the base potential of the transistor 22 to which thevoltage divided through the resistor 27 and zener diode 28 is applied iskept constant at a relatively small value. Now, since the emitter of thetransistor 22 is connected to the power line 24 via a resistor 23, thecollector current takes the form of a constant current from which thecapacitor 26 is charged. Under this condition, when a positive pulsevoltage is applied to the terminal 39 from generator 4 at a desired timeso as to restart the fuel injection, the transistor 35 is renderedconductive and the charge across the capacitor 26 is discharged toground via the diode 37 and the transistor 35. As a result, the timesignal voltage E at the output terminal 25 becomes zero. Then, when thetransistor 35 becomes nonconducting, the capacitor 26 is charged by theconstant collector current of the transistor 22, the terminal voltage isincreased, and the time signal voltage E is delivered as a function oftime from the time signal output terminal 25.

Following this operation, when the engine manifold negative pressure Pis'reduced below the set value P,, the diaphragm device 33 is actuatedto close the switch 32, the resistor 31 is connected in parallel to thevoltage dividing resistor 29, and the terminal voltage of the resistor31 is reduced. The reduced value of this terminal voltage serves toincrease the base potential of the transistor 22. Consequently, the setvalue of the constant current flowing in the collector of the transistor22 is reduced, the voltage charge across the capacitor 26 (namely, theoutput voltage E at the output terminal 25) is also reduced, and thusthe time signal current conversion from I, to I, occurs, as shown inFIG. 7(a). However, with this operation, the voltage variation at thevoltage dividing point of the resistors 29 and 30 is not changedabruptly, but is delayed by the capacitor 34. In other words, bysuitably determining the value of the capacitor 34, it becomes possibleto smoothly change over the fuel feed characteristics without causingshock.

In the foregoing circuit an Esaki diode and transistors are used as theadding level detector 6. Instead, a circuit, such as an operationalamplifier circuit, capable of adding a plurality of input signals, suchas a conditional signal or signals and a time signal, may be used as thelevel detecting circuit 6 with the present invention, or a circuit inwhich either the time signal or conditional signal is used for biasingthe detected level may be used.

Also, the time signal generating means used for the above-describedembodiment may be modified according to the requirements of a particularapplication other than the one mentioned herein.

According to this invention, as has been described, the conversioncoefficient of the time signal versus time lapse is changed by the useof a specific engine manifold negative pressure, and thus the fuel feedcharacteristics can be compensated by simple procedures.

While the principles of the invention have been described above inconnection with a specific embodiment and particular modificationsthereof, it is to be clearly understood that this description is madeonly by way of example and not as a limitation on the scope of theinvention.

What is claim is: 1. A fuel feed control system for controlling thesupply of fuel fed to an engine in accordance with at least one engineoperating condition, comprising condition detecting means for generatingan electrical condition signal corresponding to the level of enginemanifold pressure,

timing means for periodically generating a timing signal having alinearly increasing amplitude with time, and

level detecting means responsive to the sum of said condition and timingsignals for generating a fuel control signal whose duration equals thetime required for the sum of said condition and timing signals to reacha prescribed value,

said timing means including control means responsive to one given valueof engine manifold pressure forming a critical point between theeconomical output region and the high output region of the engineoperating characteristic for adjusting the rate of change of said timingsignal from a first value to a second value.

2. A fuel feed control system as defined in claim 1, wherein said leveldetecting means includes summing means for summing said condition signaland said timing signal and switching means responsive to said summedsignal value for providing said fuel control signal for all levels ofsaid summed signal value below a given limit.

3. A fuel feed control system as defined in claim 2, wherein saidcondition detecting means generates a plurality of condition signalsrelating to different engine conditions and said summing means sums allof said condition signals with said timing signal.

4. A fuel feed control system as defined in claim 1, wherein saidcontrol means in said timing means includes delay means for graduallyadjusting the rate of change of said timing signal upon detection ofsaid given value of engine manifold pressure.

5. A fuel feed control system as defined in claim 4, wherein said timingmeans includes a pulse generator and a timing signal generating circuitresponsive to the output of said pulse generator for generating asawtooth wave timing signal.

6. A fuel feed control system as defined in claim 5, wherein said timingsignal generating circuit includes a timing capacitor connected to aconstant current source and means responsive to the output of said pulsegenerator for periodically discharging said timing capacitor, saidcontrol means including means responsive to said change'in enginemanifold pressure for changing the level of the current generated bysaid constant current source.

7. A fuel feed control system as defined in claim 6, wherein said leveldetecting means includes summing means for summing said condition signaland said timing signal and switching means responsive to said summedsignal value for providing said fuel control signal for all levels ofsaid summed signal value below a given limit.

8. A fuel feed control system as defined in claim 7, wherein saidcondition detecting means generates a plurality of condition signalsrelating to different engine conditions and said summary means sums allof said condition signals with said timing signal.

9. A fuel feed control system as defined in claim 1, wherein said leveldetecting means comprises a plurality of resistances connecting aplurality of input terminals to a common summing point, an Esaki diodeconnected between said summing point and ground, and a transistor havingits base connected to said summing point, its collector connectedthrough a resistance to a power source and its emitter connected toground, said timing means being connected to apply said timing signal toone of said input terminals and said condition detecting means applyinga plurality of condition signals relating to different engine conditionsto the remaining input terminals.

10. A fuel feed control system as defined in claim 9, wherein saidtiming means comprises a timing capacitor connected in series with atransistor constant current source, a pulse generator, a transistorswitch connected to said pulse generator and said timing capacitor forperiodically discharging said timing capacitor, and means for changingthe level of said constant current source including a delay capacitorfor effecting a delay in the change of current level of said constantcurrent source.

l l. A fuel feed control system for controlling the supply of fuel fedto an engine in accordance with at least one engine operating condition,comprising condition detecting means for generating an electricalcondition signal corresponding to said engine operating condition, saidcondition signal corresponding to a condition selected from the groupconsisting of manifold pressure, engine temperature and engine speed,

timing means for periodically generating a timing signal having alinearly increasing amplitude with time, said timing means including apulse generator and a timing signal generating circuit responsive to theoutput of said pulse generator for generating a sawtooth wave timingsignal, and

level detecting means responsive to the sum of said condition and timingsignals for generating a fuel control signal whose duration equals thetime required for the sum of said condition and timing signals to reacha prescribed value,

said timing means further including control means responsive to onegiven value of engine manifold pressure forming a critical point betweenthe economical output region and the high output region of the engineoperating characteristic for adjusting the rate of change of said timingsignal from a first value for said economical output region to a secondvalue for said high output region, said control means including delaymeans for gradually transferring the rate of said timing signal upondetection of said critical point from said first value for saideconomical output region to said second value for said high outputregion.

1. A fuel feed control system for controlling the supPly of fuel fed toan engine in accordance with at least one engine operating condition,comprising condition detecting means for generating an electricalcondition signal corresponding to the level of engine manifold pressure,timing means for periodically generating a timing signal having alinearly increasing amplitude with time, and level detecting meansresponsive to the sum of said condition and timing signals forgenerating a fuel control signal whose duration equals the time requiredfor the sum of said condition and timing signals to reach a prescribedvalue, said timing means including control means responsive to one givenvalue of engine manifold pressure forming a critical point between theeconomical output region and the high output region of the engineoperating characteristic for adjusting the rate of change of said timingsignal from a first value to a second value.
 2. A fuel feed controlsystem as defined in claim 1, wherein said level detecting meansincludes summing means for summing said condition signal and said timingsignal and switching means responsive to said summed signal value forproviding said fuel control signal for all levels of said summed signalvalue below a given limit.
 3. A fuel feed control system as defined inclaim 2, wherein said condition detecting means generates a plurality ofcondition signals relating to different engine conditions and saidsumming means sums all of said condition signals with said timingsignal.
 4. A fuel feed control system as defined in claim 1, whereinsaid control means in said timing means includes delay means forgradually adjusting the rate of change of said timing signal upondetection of said given value of engine manifold pressure.
 5. A fuelfeed control system as defined in claim 4, wherein said timing meansincludes a pulse generator and a timing signal generating circuitresponsive to the output of said pulse generator for generating asawtooth wave timing signal.
 6. A fuel feed control system as defined inclaim 5, wherein said timing signal generating circuit includes a timingcapacitor connected to a constant current source and means responsive tothe output of said pulse generator for periodically discharging saidtiming capacitor, said control means including means responsive to saidchange in engine manifold pressure for changing the level of the currentgenerated by said constant current source.
 7. A fuel feed control systemas defined in claim 6, wherein said level detecting means includessumming means for summing said condition signal and said timing signaland switching means responsive to said summed signal value for providingsaid fuel control signal for all levels of said summed signal valuebelow a given limit.
 8. A fuel feed control system as defined in claim7, wherein said condition detecting means generates a plurality ofcondition signals relating to different engine conditions and saidsummary means sums all of said condition signals with said timingsignal.
 9. A fuel feed control system as defined in claim 1, whereinsaid level detecting means comprises a plurality of resistancesconnecting a plurality of input terminals to a common summing point, anEsaki diode connected between said summing point and ground, and atransistor having its base connected to said summing point, itscollector connected through a resistance to a power source and itsemitter connected to ground, said timing means being connected to applysaid timing signal to one of said input terminals and said conditiondetecting means applying a plurality of condition signals relating todifferent engine conditions to the remaining input terminals.
 10. A fuelfeed control system as defined in claim 9, wherein said timing meanscomprises a timing capacitor connected in series with a transistorconstant current source, a pulse generator, a transistor switchconnected to said pulse generator and said timing capacitor forperiodically discharging said timing capacitor, and meAns for changingthe level of said constant current source including a delay capacitorfor effecting a delay in the change of current level of said constantcurrent source.
 11. A fuel feed control system for controlling thesupply of fuel fed to an engine in accordance with at least one engineoperating condition, comprising condition detecting means for generatingan electrical condition signal corresponding to said engine operatingcondition, said condition signal corresponding to a condition selectedfrom the group consisting of manifold pressure, engine temperature andengine speed, timing means for periodically generating a timing signalhaving a linearly increasing amplitude with time, said timing meansincluding a pulse generator and a timing signal generating circuitresponsive to the output of said pulse generator for generating asawtooth wave timing signal, and level detecting means responsive to thesum of said condition and timing signals for generating a fuel controlsignal whose duration equals the time required for the sum of saidcondition and timing signals to reach a prescribed value, said timingmeans further including control means responsive to one given value ofengine manifold pressure forming a critical point between the economicaloutput region and the high output region of the engine operatingcharacteristic for adjusting the rate of change of said timing signalfrom a first value for said economical output region to a second valuefor said high output region, said control means including delay meansfor gradually transferring the rate of said timing signal upon detectionof said critical point from said first value for said economical outputregion to said second value for said high output region.